# US 10,871,188 B2 · Control method and control device for magnetic bearing

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- Number: US 10,871,188 B2
- Document ID: US10871188B2
- Status: Granted
- Kind: B2
- Application number: 15/574,964
- Filed: 2016-05-27
- Published: 2018-06-21
- Granted: 2020-12-22
- Earliest claimed: 2015-05-27
- Assignees: Gree Green Refrigeration Technology Center Co., Ltd. of Zhuhai
- Applicants: Gree Green Refrigeration Technology Center Co., Ltd of Zhuhai
- Inventors: Daofu Hu; Yusheng Hu; Weilin Guo; Yongling He; Bin Yang; Xue Li
- Web page: https://patentgrep.com/patent/US10871188B2

## CPC

- F16C 32/0444: {Details of devices to control the actuation of the electromagnets}
- F16C 32/0442: {with devices affected by abnormal, undesired or non-standard conditions such as shock-load, power outage, start-up or touchdown}
- F16C 32/0451: {Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control}
- F16C 32/0453: {for controlling two axes, i.e. combined control of x-axis and y-axis}
- F16C 32/0457: {Details of the power supply to the electromagnets}
- F16C 39/06: using magnetic means
- H02K 7/09: with magnetic bearings
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A control method for a magnetic bearing includes following steps: acquiring a suspension stopping instruction for the magnetic bearing, and respectively applying a control current to one or more control coils of the magnetic bearing to subject a rotor to a vertically or obliquely upwards electromagnetic force, a vertical component of the electromagnetic force is less than the gravity of the rotor. A control device for a magnetic bearing is also disclosed, including a suspension stopping instruction acquiring unit and a control current applying unit. The control method and control device for a magnetic bearing can control a falling velocity of the rotor to be lower than that of the rotor being subjected only to the gravity, and have higher control efficiency.

## Claims

### Claim 1

A control method for a magnetic bearing, comprising following steps:
acquiring a suspension stopping instruction for the magnetic bearing, and
applying a control current to a control coil of the magnetic bearing to subject a rotor of the magnetic bearing to a vertically or obliquely upwards electromagnetic force, a vertical component of the electromagnetic force is less than the gravity of the rotor;
wherein the control current is gradually decreased to allow a vertical resultant force exerted on the rotor to be gradually increased.

### Claim 2 (depends on 1)

The control method of claim 1, wherein a value of each control current Ix is calculated based on an equation Ix=Px×S+ix until the value of each control current Ix is zero;
wherein Px is a slope coefficient of switching each control current Ix, Px=(0-ix)/A, ix is an initial value of each control current Ix, A is a number of switching times of each control current Ix, S is a number of iterations and has an initial value of zero, each control current Ix is switched for every period T, a value of a period timer is n with an initial value of zero, and n is continuously accumulated, when n<T, S remains constant, when n=T, then S=S+1 and n is cleared, x is an integer greater than or equal to 1.

### Claim 3 (depends on 2)

The control method of claim 2, wherein the step of applying a control current to a control coil of the magnetic bearing includes applying control currents to two control coils of the magnetic bearing, respectively;
the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through a shaft center of the rotor;
the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 4 (depends on 3)

The control method of claim 3, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.

### Claim 5 (depends on 1)

The control method of claim 1, wherein the step of applying a control current to a control coil of the magnetic bearing includes applying control currents to two control coils of the magnetic bearing, respectively;
the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through a shaft center of the rotor; the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 6 (depends on 5)

The control method of claim 5, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.

### Claim 7 (depends on 5)

The control method of claim 5, wherein an angle between a direction of the first electromagnetic force and a gravitational direction of the rotor is more than 90°, and less than or equal to 180°, an angle between a direction of the second electromagnetic force and the gravitational direction of the rotor is more than 90°, and less than or equal to 180°.

### Claim 8 (depends on 1)

The control method of claim 1, wherein the step of applying a control current to a control coil of the magnetic bearing includes applying control currents to two control coils of the magnetic bearing, respectively;
the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through a shaft center of the rotor;
the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 9 (depends on 8)

The control method of claim 8, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.

### Claim 10

A control device for a magnetic bearing, comprising a suspension stopping instruction acquiring unit and a control current applying unit;
the suspension stopping instruction acquiring unit is configured to acquire a suspension stopping instruction for the magnetic bearing;
the control current applying unit is configured to apply a control current to one or more control coils of the magnetic bearing, respectively, to subject the rotor to a vertically or obliquely upwards electromagnetic force, a vertical component of the electromagnetic force is less than gravity of the rotor;
wherein the control current is gradually decreased to allow a vertical resultant force exerted on the rotor to be gradually increased.

### Claim 11 (depends on 10)

The control device of claim 10, wherein the control device further comprises a control current calculating unit, the control current calculating unit is configured to calculate the control current, and send calculation results to the control current applying unit, the control current applying unit is configured to apply the control current to the one or more control coils of the magnetic bearing, respectively;
the control current calculating unit is configured to calculate a value of each control current h based on an equation Ix=Px×S+ix until the value of each control current Ix is zero;
wherein Px is a slope coefficient for switching each control current Ix, Px=(0-ix)/A, ix is an initial value of each control current Ix, A is a number of switching times of each control current Ix, S is a number of iterations and has an initial value of zero, each control current Ix is switched for every period T, a value of a period timer is n with an initial value of zero, and n is continuously accumulated, when n<T, S remains constant, when n=T, then S=S+1 and n is cleared, x is an integer greater than or equal to 1.

### Claim 12 (depends on 11)

The control device of claim 11, wherein the control currents are applied to two control coils of the magnetic bearing, respectively, the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through the shaft center of the rotor; the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 13 (depends on 12)

The control device of claim 12, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.

### Claim 14 (depends on 10)

The control device of claim 10, wherein the control currents are applied to two control coils of the magnetic bearing, respectively, the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through the shaft center of the rotor; the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 15 (depends on 14)

The control device of claim 14, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.

### Claim 16 (depends on 14)

The control device of claim 14, wherein an angle between a direction of the first electromagnetic force and a gravitational direction of the rotor is more than 90°, and less than or equal to 180°, an angle between a direction of the second electromagnetic force and the gravitational direction of the rotor is more than 90°, and less than or equal to 180°.

### Claim 17 (depends on 10)

The control device of claim 10, wherein the control currents are applied to two control coils of the magnetic bearing, respectively, the two control coils are a first coil and a second coil, the first coil and the second coil are symmetrical with respect to the vertical line passing through the shaft center of the rotor;
the control current applied to the first control coil subjects the rotor to a first electromagnetic force, the control current applied to the second control coil subjects the rotor to a second electromagnetic force, a resultant force of the first electromagnetic force and the second electromagnetic force is the electromagnetic force.

### Claim 18 (depends on 17)

The control device of claim 17, wherein the control currents applied to the first control coil and the second control coil have the same magnitude.